Similar to Si_(3)N_(4)ceramics,β→a phase transformation in SiC ceramics plays a key role in tailoring the microstructures thus optimizing related properties.SiC microstructures are dominated with the core erim struc...Similar to Si_(3)N_(4)ceramics,β→a phase transformation in SiC ceramics plays a key role in tailoring the microstructures thus optimizing related properties.SiC microstructures are dominated with the core erim structures by AlN-solution,and by EBSD analysis,a-lamellae were revealed as stacking-faults(SF)and twin-boundaries(TB)in b-grains,co-existing with the coreerim structures asα/β→α’/β’transformation by sintering.The structural transformation can proceed much further by gas-pressuresintering than hot-pressing with only RE2O3 agents,while the latter retain a high-density of SF/TB in the metastable b-SiC grains.By high-angle secondary-electron imaging,nanoscale transition-layer(TL)was observed as an inter-phase to fully separate the core and rim,which is created by a transitory equilibrium in the solutionereprecipitation process.The enrichment of AlN or RE in TL demonstrates their segregation to core surface until reaching the super-saturation and before the growth of rims.With higher AlN or RE solution and after sintering,a shear stress can develop from TL contour to drive the expansion of SF/TB in Martensitic transition,especially under an external isotropic pressure.The combinations ofβ→a transformation,coreerim structures and viscous liquid-phase enable the comprehensive assessment of sintering-microstructure-property-performance relationship of SiC ceramics,as demonstrated for their creep behaviors and fracture toughness.展开更多
Biomorphic （wood derived） carbide ceramics with an overall composition in the SiC/C was produced by supereritical ethanol infiltration of low viscosity tetraethylorthosilicate/supercritical ethanol into biologically...Biomorphic （wood derived） carbide ceramics with an overall composition in the SiC/C was produced by supereritical ethanol infiltration of low viscosity tetraethylorthosilicate/supercritical ethanol into biologically derived carbon templates （CB-templates） and in situ hydrolysis into Si（OH）4-gel, the Si（OH）4-gel was calcined at 1400℃ to promote the polycondensation of Si（OH）4-gel into SiO2-phase and then carbonthermal reduction of the SiO2 with the biocarbon template into highly porous, biomorphic SiC/C ceramics. The phases and morphology conversion mechanism of resulting porous SiC/C ceramics have been investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Fourier transform infrared spectroscopy （FT-IR）. Experimental results showed that the biomorphic cellular morphology of pinewood charcoal was remained in the porous SiC/C ceramic with high precision that consisted of β-SiC with minority of α-SiC and the remain free carbon existed in amorphous phase.展开更多
Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is ...Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is studied.Experimental results show that the vickers hardness,wear resistance and thermal conductivity of the samples increase with the increase in the SiC content,and the hardness of the sample reaches 16.22 GPa,and thermal conductivity of the sample reaches 25.41 W/(m.K)at room temperature when the SiC content is 20 wt%(B5)and the sintering temperature is at 1640℃.Higher hardness means higher scour resistance,and it indicates that the B5 material is expected to be used for the solar heat absorber of third generation solar thermal generation.The results indicate the mechanism of improving mechanical properties of Al_(2)O_(3)/SiC composite ceramics:SiC plays a role in grain refinement that the grain of SiC inhibits the grain growth of Al_(2)O_(3),while the addition of SiC changes the fracture mode from the intergranular to the intergranular-transgranular.展开更多
SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum ...SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.展开更多
Silicon carbide ceramics were prepared with SiC powder treated by the fluidized bed opposed jet mill as raw materials, and the effects of the ultra-fine treatment mechanism on the compaction and sintering behavior of ...Silicon carbide ceramics were prepared with SiC powder treated by the fluidized bed opposed jet mill as raw materials, and the effects of the ultra-fine treatment mechanism on the compaction and sintering behavior of SiC ceramics were investigated. The results showed that the compacts had higher density and microstructure homogeneity when the sintering temperature of the compact was decreased; and that the surface microstructure, densification and mechanical properties of the sintered body could be ameliorated obviously.展开更多
In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In...In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.展开更多
Si/SiC ceramic composite and lnvar alloy were successfidly joined by vacuum brazing using Ti5OCu-W filler metals into which W was added to release the thermal stress of the brazed joint. Microstructures of the brazed ...Si/SiC ceramic composite and lnvar alloy were successfidly joined by vacuum brazing using Ti5OCu-W filler metals into which W was added to release the thermal stress of the brazed joint. Microstructures of the brazed joints were irwestigated by scanning electron micrascope （SEM） and energy dispersive spectrometer （EDS）. The mechanical properties of the brazed joints were measured by shearing tests. The results showed that the brazed joints were composed of Ti-Cu phase, W phase and Ti-Si phase. W had no effect on the wettability and mobility of the .filler metals. The growth of Ti2 Cu phase was restrained, and the reaction between ceramic composite and filler metals was weakened. The specimen, brazed at 970°C for 5 rain, had the maximum shear strength of 108 MPa at room temperature.展开更多
Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperature...Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperatures ranging from 1 100 ℃ to 1 300 ℃. Three point bending strength of the joint reached the maximum of 179 MPa as joined at 1 200℃. The joining layer is continuous, homogeneous and densified and has a thickness of 2 μm -5μm. The joining mechanism is that the amorphous silicon oxycarbide （SixOyCz） ceramic pyrolyzed from silicon resin YR3370 acts as an inorganic adhesive to SSiC substrate, which means the formation of the continuous Si-C bond structure between SixOyCz structure and SSiC substrate. Life prediction of the ceramic joint can be realized through the measurement of the critical time of the joint after the cyclic loading test.展开更多
A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybr...A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.展开更多
The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those o...The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.展开更多
Fabricating SiC ceramics via the digital light processing(DLP)technology is of great challenge due to strong light absorption and high refractive index of deep-colored SiC powders,which highly differ from those of res...Fabricating SiC ceramics via the digital light processing(DLP)technology is of great challenge due to strong light absorption and high refractive index of deep-colored SiC powders,which highly differ from those of resin,and thus significantly affect the curing performance of the photosensitive SiC slurry.In this paper,a thin silicon oxide(SiO_(2))layer was in-situ formed on the surface of SiC powders by pre-oxidation treatment.This method was proven to effectively improve the curing ability of SiC slurry.The SiC photosensitive slurry was fabricated with solid content of 55 vol%and viscosity of 7.77 Pa·s(shear rate of 30 s^(−1)).The curing thickness was 50μm with exposure time of only 5 s.Then,a well-designed sintering additive was added to completely convert low-strength SiO_(2) into mullite reinforcement during sintering.Complexshaped mullite-bond SiC ceramics were successfully fabricated.The flexural strength of SiC ceramics sintered at 1550℃in air reached 97.6 MPa with porosity of 39.2 vol%,as high as those prepared by spark plasma sintering(SPS)techniques.展开更多
In this study,C_(f)/SiC composites with excellent mechanical and thermal properties were prepared by combining binder jetting(BJ)additive manufacturing with liquid silicon infiltration(LSI)process.The introduction of ...In this study,C_(f)/SiC composites with excellent mechanical and thermal properties were prepared by combining binder jetting(BJ)additive manufacturing with liquid silicon infiltration(LSI)process.The introduction of C_(f)into the C_(f)/SiC mixed powder reduced its spreading ability,which reduced the density,strength,and precision of the C_(f)/SiC green parts.However,phenolic resin infiltration and pyrolysis(PRIP)treatment compensated for the decrease in the density of the green parts resulting from the introduction of C_(f).By optimizing the number of PRIP cycles to increase the pyrolytic carbon(PyC)content in the carbonized parts,the C_(f)in the green parts successfully prevented the reaction with molten Si in the LSI and played an important role in strengthening and toughening the composites.The flexural strength,fracture toughness,and thermal conductivity of the C_(f)/SiC composites reached the maximum values of 316±16 MPa,4.81±0.12 MPa·m1/2,and 140 W/m·K,respectively.This study presents future opportunities for the cost-effective and efficient industrial manufacturing of C_(f)/SiC complex structures.展开更多
Achieving high-quality joining of silicon carbide(SiC)ceramics and Inconel 718 alloy has become a significant challenge for the brazing process,which is strongly dependent on the filler material.A novel composite inte...Achieving high-quality joining of silicon carbide(SiC)ceramics and Inconel 718 alloy has become a significant challenge for the brazing process,which is strongly dependent on the filler material.A novel composite interlayer consisting of high-entropy alloys(HEAs),HEA/Ni/HEA,was proposed to reduce the formation of intermetallic compounds in the brazed joints of SiC ceramics and Inconel 718 alloy.A reliable SiC/Inconel 718 brazed joint was produced at 1120℃ for 60 min.The results showed a significant reduction in the number of NiSi compounds in the brazed joint.The brazing seam structure near SiC side was filled with face-centered cubic phases with good plasticity and soft Cu-rich phases due to the high-entropy effect,which effectively suppressed the formation of intermetallic compounds.The maximum shear strength of the brazed joint reached 88 MPa,showing excellent tensile strength.The results provide a valuable basis for improving the joint quality of SiC ceramics and metals by adding high-entropy alloy fillers.展开更多
A novel super-hybrid composite (NSHC) was boron-modified phenolic resin (BPR) with three-dimensional reticulated SiC ceramic (3DRC) and high silica fibers. Ablation performance of the NSHC was studied. The results sho...A novel super-hybrid composite (NSHC) was boron-modified phenolic resin (BPR) with three-dimensional reticulated SiC ceramic (3DRC) and high silica fibers. Ablation performance of the NSHC was studied. The results show that the linear ablation rate of NSHC was lower than that of pure BPR and the high silica/BPR composite. Its linear ablation rate is 1/17 of the high silica/BPR. Mass ablation rate of the NSHC is very close to that of the pure BPR and the high silica/BPR composite. Scanning electron microscope (SEM) analysis indicates that 3DRC has scarcely changed its shape at the ablation temperature. Its special reticulated structure can restrict the materials deformation and prevent high velocity heat flow from eroding the surface of the materials largely and thus increase ablation resistance of the NSHC.展开更多
Porous ceramics usually require high mechanical strength and maximized porosity simultaneously,while for conventional particle grading strategies,it is highly challenging to meet both demands.To this end,a reverse par...Porous ceramics usually require high mechanical strength and maximized porosity simultaneously,while for conventional particle grading strategies,it is highly challenging to meet both demands.To this end,a reverse particle grading strategy was developed based on the linear packing model by unusually introducing coarse particles(d_(50)=16μm)into a fine particle(d50=5μm)matrix.Following the extrusion and sintering process,tubular porous SiC ceramic supports with improved mechanical strength were successfully fabricated.The effects of coarse particles on the rheological properties of the ceramic paste and the macroscopic properties and microstructure of the SiC supports were systematically investigated.With an increase in the content of coarse SiC particles to 30 wt%,the pressure generated during extrusion decreased from 5.5±0.2 to 1.3±0.1 MPa.Notably,the bending strength of the tubular supports increased from 36.6±5.6 to 49.1±4.5 MPa when 20 wt%coarse powder was incorporated.The notably improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection.Additionally,the optimized tubular supports had an average pore size of 1.2±0.1μm,an open porosity of 45.1%±1.6%,and a water permeability of 7163±150 L/(m^(2)·h·bar)as well as good alkali and acid corrosion resistance.Significantly,the strategy was proven to be feasible for the scale-up fabrication of 19-channel SiC tubular porous ceramic supports.展开更多
This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the cerami...This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.展开更多
This study focused on producing metal matrix composite(MMC)coatings on Ti–6Al–4V alloy through laser surface alloying using a novel combination of Inconel 625 and SiC precursor materials.Various ratios of alloying p...This study focused on producing metal matrix composite(MMC)coatings on Ti–6Al–4V alloy through laser surface alloying using a novel combination of Inconel 625 and SiC precursor materials.Various ratios of alloying powders were examined to evaluate surface properties such as microhardness,wear resistance,and friction coefficient,along with analyzing the phase composition and microstructure of the coatings.The in situ synthesized MMC coatings exhibited the presence ofα-Ti,NiTi,NiTi_(2),and TiC phases.Additionally,Ti_(5)Si_(3)andα-Ti/Ti_(5)Si_(3)eutectic structures were observed when the SiC content exceeded 20%.In comparison to the titanium substrate,the MMC coating significantly enhanced microhardness by over threefold and reduced wear by 95%.However,it was crucial to carefully select the appropriate combination of alloying powders to avoid a substantial decrease in friction performance and excessive formation of cracks.Through a comparative analysis of experimental results,the optimal precursor material composition was identified as 85%Inconel 625 and 15%SiC.This study demonstrated the effective utilization of Inconel 625 and SiC alloying materials to enhance the surface properties of titanium alloys,thereby expanding their application in challenging environments.展开更多
Different semiconductive SiC foam supports were prepared by varying the sintering temperature and atmosphere, and with or without alkaline solution treatment and high temperature oxidation following a macromolecule py...Different semiconductive SiC foam supports were prepared by varying the sintering temperature and atmosphere, and with or without alkaline solution treatment and high temperature oxidation following a macromolecule pyrogenation combined with reaction bonding method. Nano-TiO2 particles were immobilized onto these SiC foam supports by a composite sol-gel method. The phase, surface morphology, the type of conduction and the photocatalytic activity of the TiO2-SiC composite photocatalysts were studied. The TiO2 coated on p-type Si-free SiC support showed the highest photocatalytic efficiency in degradation of 4- aminobenzenesulfonic acid （4-ABS） in aqueous solution as compared to that coated on n-type SiC support and p-type SiC supports with residual Si or Si02 on the surface. The result showed that the TiO2 coatings immobilized on p-type semiconductive SiC foam supports exhibited obviously higher photocatalytic activity in comparison to that coated on n-type SiC foam support. The p-n heterojunctions formed between the p-type SiC supports and n-type TiO2 coatings might be able to account for the better charge separation and transfer as well as the photocatalytic activity of the TiO2-SiC composite photocatalyst.展开更多
Model composites consisting of SiC fiber and Yb_(2)SiO_(5)were processed by the spark plasma sintering(SPS)method.The mechanical compatibility and chemical stability between Yb_(2)SiO_(5)and SiC fiber were studied to ...Model composites consisting of SiC fiber and Yb_(2)SiO_(5)were processed by the spark plasma sintering(SPS)method.The mechanical compatibility and chemical stability between Yb_(2)SiO_(5)and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite(SiC_(f)/SiC CMC).Two kinds of interfaces,namely mechanical and chemical bonding interfaces,were achieved by adjusting sintering temperature.SiC_(f)/Yb_(2)SiO_(5)interfaces prepared at 1450 and 1500℃exhibit high interface strength and debond energy,which do not satisfy the crack deflection criteria based on He-Hutchison diagram.Raman spectrum analyzation indicates that the thermal expansion mismatch between Yb_(2)SiO_(5)and SiC contributes to high compressive thermal stress at interface,and leads to high interfacial parameters.Amorphous layer at interface in model composite sintered at 1550℃is related to the diffusion promoted by high temperature and DC electric filed during SPS.It is inspired that the interfacial parameters could be adjusted by introducing Yb_(2)Si_(2)O_(7)-Yb_(2)SiO_(5)interphase with controlled composition to optimize the mechanical fuse mechanism in SiC_(f)/SiC CMC.展开更多
Carbide ceramic fibers are of significant importance for application in the high-tech areas of advanced aircraft engines,aerospace vehicles,and the nuclear industry due to their excellent properties,such as high tensi...Carbide ceramic fibers are of significant importance for application in the high-tech areas of advanced aircraft engines,aerospace vehicles,and the nuclear industry due to their excellent properties,such as high tensile strength and elastic modulus,excellent high-temperature resistance,and oxidation resistance.This paper reviews the preparation and application of different carbide ceramic fibers,including SiC fibers and transition metal carbide(e.g.,ZrC,HfC,and TaC)ceramic fibers.The preparation methods of carbide ceramic fibers are discussed in terms of different fiber diameters,represented by SiC fibers with variable weaving properties and functions due to their differences in diameter.Subsequently,the application of carbide ceramic fibers as high-temperature-resistant structural materials,catalyst carriers,sensors,and supercapacitors are summarized,and strategies for the future development of carbide ceramic fibers are proposed.This review aims to help researchers enhance their understanding of the preparation and utilization of carbide ceramic micro/nanofibers,advancing the development of high-performance carbide ceramic fibers.展开更多
基金supported by the National Natural Science Foundation(Grant Nos.51532006 and 52032002)Shanghai Technical Service Center for Advanced Ceramics Structure Design and Precision Manufacturing(Grant No.20DZ2294000)supported provisionally by the Max-Planck Gesellschaft via the Max-Plack Partner Group in Shanghai Institute of Ceramics,Chinese Academy of Sciences through the years of 2003e2008.
文摘Similar to Si_(3)N_(4)ceramics,β→a phase transformation in SiC ceramics plays a key role in tailoring the microstructures thus optimizing related properties.SiC microstructures are dominated with the core erim structures by AlN-solution,and by EBSD analysis,a-lamellae were revealed as stacking-faults(SF)and twin-boundaries(TB)in b-grains,co-existing with the coreerim structures asα/β→α’/β’transformation by sintering.The structural transformation can proceed much further by gas-pressuresintering than hot-pressing with only RE2O3 agents,while the latter retain a high-density of SF/TB in the metastable b-SiC grains.By high-angle secondary-electron imaging,nanoscale transition-layer(TL)was observed as an inter-phase to fully separate the core and rim,which is created by a transitory equilibrium in the solutionereprecipitation process.The enrichment of AlN or RE in TL demonstrates their segregation to core surface until reaching the super-saturation and before the growth of rims.With higher AlN or RE solution and after sintering,a shear stress can develop from TL contour to drive the expansion of SF/TB in Martensitic transition,especially under an external isotropic pressure.The combinations ofβ→a transformation,coreerim structures and viscous liquid-phase enable the comprehensive assessment of sintering-microstructure-property-performance relationship of SiC ceramics,as demonstrated for their creep behaviors and fracture toughness.
基金Financial supports by National Science Foundation of China （No. 40602008） Research Fund of National Laboratory of Mineral Materials （No. 05005A） are gratefully acknowledged.
文摘Biomorphic （wood derived） carbide ceramics with an overall composition in the SiC/C was produced by supereritical ethanol infiltration of low viscosity tetraethylorthosilicate/supercritical ethanol into biologically derived carbon templates （CB-templates） and in situ hydrolysis into Si（OH）4-gel, the Si（OH）4-gel was calcined at 1400℃ to promote the polycondensation of Si（OH）4-gel into SiO2-phase and then carbonthermal reduction of the SiO2 with the biocarbon template into highly porous, biomorphic SiC/C ceramics. The phases and morphology conversion mechanism of resulting porous SiC/C ceramics have been investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Fourier transform infrared spectroscopy （FT-IR）. Experimental results showed that the biomorphic cellular morphology of pinewood charcoal was remained in the porous SiC/C ceramic with high precision that consisted of β-SiC with minority of α-SiC and the remain free carbon existed in amorphous phase.
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2018YFB1501002)。
文摘Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is studied.Experimental results show that the vickers hardness,wear resistance and thermal conductivity of the samples increase with the increase in the SiC content,and the hardness of the sample reaches 16.22 GPa,and thermal conductivity of the sample reaches 25.41 W/(m.K)at room temperature when the SiC content is 20 wt%(B5)and the sintering temperature is at 1640℃.Higher hardness means higher scour resistance,and it indicates that the B5 material is expected to be used for the solar heat absorber of third generation solar thermal generation.The results indicate the mechanism of improving mechanical properties of Al_(2)O_(3)/SiC composite ceramics:SiC plays a role in grain refinement that the grain of SiC inhibits the grain growth of Al_(2)O_(3),while the addition of SiC changes the fracture mode from the intergranular to the intergranular-transgranular.
基金Funded by the National Key R&D Program of China(No.2018YFB1501002)。
文摘SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.
文摘Silicon carbide ceramics were prepared with SiC powder treated by the fluidized bed opposed jet mill as raw materials, and the effects of the ultra-fine treatment mechanism on the compaction and sintering behavior of SiC ceramics were investigated. The results showed that the compacts had higher density and microstructure homogeneity when the sintering temperature of the compact was decreased; and that the surface microstructure, densification and mechanical properties of the sintered body could be ameliorated obviously.
基金the National Natural Science Foundation of China(Grant No.51964022).
文摘In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.
文摘Si/SiC ceramic composite and lnvar alloy were successfidly joined by vacuum brazing using Ti5OCu-W filler metals into which W was added to release the thermal stress of the brazed joint. Microstructures of the brazed joints were irwestigated by scanning electron micrascope （SEM） and energy dispersive spectrometer （EDS）. The mechanical properties of the brazed joints were measured by shearing tests. The results showed that the brazed joints were composed of Ti-Cu phase, W phase and Ti-Si phase. W had no effect on the wettability and mobility of the .filler metals. The growth of Ti2 Cu phase was restrained, and the reaction between ceramic composite and filler metals was weakened. The specimen, brazed at 970°C for 5 rain, had the maximum shear strength of 108 MPa at room temperature.
基金National Key Fundamental R&D Plan (2004CB217808)National Natural Science Foundation of China (20271037)
文摘Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （GE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperatures ranging from 1 100 ℃ to 1 300 ℃. Three point bending strength of the joint reached the maximum of 179 MPa as joined at 1 200℃. The joining layer is continuous, homogeneous and densified and has a thickness of 2 μm -5μm. The joining mechanism is that the amorphous silicon oxycarbide （SixOyCz） ceramic pyrolyzed from silicon resin YR3370 acts as an inorganic adhesive to SSiC substrate, which means the formation of the continuous Si-C bond structure between SixOyCz structure and SSiC substrate. Life prediction of the ceramic joint can be realized through the measurement of the critical time of the joint after the cyclic loading test.
文摘A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.
文摘The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.
基金supported by Shandong University−MSEA International Institute for Materials Genome Joint Innovation Center for Advanced Ceramics,and the Key Research and Development Projects of Shaanxi Province(Nos.2018ZDCXLGY-09-06 and 2021ZDLGY14-06).
文摘Fabricating SiC ceramics via the digital light processing(DLP)technology is of great challenge due to strong light absorption and high refractive index of deep-colored SiC powders,which highly differ from those of resin,and thus significantly affect the curing performance of the photosensitive SiC slurry.In this paper,a thin silicon oxide(SiO_(2))layer was in-situ formed on the surface of SiC powders by pre-oxidation treatment.This method was proven to effectively improve the curing ability of SiC slurry.The SiC photosensitive slurry was fabricated with solid content of 55 vol%and viscosity of 7.77 Pa·s(shear rate of 30 s^(−1)).The curing thickness was 50μm with exposure time of only 5 s.Then,a well-designed sintering additive was added to completely convert low-strength SiO_(2) into mullite reinforcement during sintering.Complexshaped mullite-bond SiC ceramics were successfully fabricated.The flexural strength of SiC ceramics sintered at 1550℃in air reached 97.6 MPa with porosity of 39.2 vol%,as high as those prepared by spark plasma sintering(SPS)techniques.
基金supported by National Defense Basic Scientific Research Program of China(Grant No.JCKY2022213C008)Fundamental Research Funds for the Central Universities of China(Grant No.YCJJ20230353)。
文摘In this study,C_(f)/SiC composites with excellent mechanical and thermal properties were prepared by combining binder jetting(BJ)additive manufacturing with liquid silicon infiltration(LSI)process.The introduction of C_(f)into the C_(f)/SiC mixed powder reduced its spreading ability,which reduced the density,strength,and precision of the C_(f)/SiC green parts.However,phenolic resin infiltration and pyrolysis(PRIP)treatment compensated for the decrease in the density of the green parts resulting from the introduction of C_(f).By optimizing the number of PRIP cycles to increase the pyrolytic carbon(PyC)content in the carbonized parts,the C_(f)in the green parts successfully prevented the reaction with molten Si in the LSI and played an important role in strengthening and toughening the composites.The flexural strength,fracture toughness,and thermal conductivity of the C_(f)/SiC composites reached the maximum values of 316±16 MPa,4.81±0.12 MPa·m1/2,and 140 W/m·K,respectively.This study presents future opportunities for the cost-effective and efficient industrial manufacturing of C_(f)/SiC complex structures.
基金financially supported by the National Natural Science Foundation of China(52074017)Beijing Natural Science Foundation(3232005)+3 种基金2024 BJUT Introducing Intelligence Breeding Project(2024DL01)China-CEEC Joint Education Project for Higher Education(2021113)State Key Laboratory of Advanced Brazing Filler Metals and Technology(SKLABFMT202004)State Key Laboratory of Advanced Welding and Joining(AWJ-20-M01).
文摘Achieving high-quality joining of silicon carbide(SiC)ceramics and Inconel 718 alloy has become a significant challenge for the brazing process,which is strongly dependent on the filler material.A novel composite interlayer consisting of high-entropy alloys(HEAs),HEA/Ni/HEA,was proposed to reduce the formation of intermetallic compounds in the brazed joints of SiC ceramics and Inconel 718 alloy.A reliable SiC/Inconel 718 brazed joint was produced at 1120℃ for 60 min.The results showed a significant reduction in the number of NiSi compounds in the brazed joint.The brazing seam structure near SiC side was filled with face-centered cubic phases with good plasticity and soft Cu-rich phases due to the high-entropy effect,which effectively suppressed the formation of intermetallic compounds.The maximum shear strength of the brazed joint reached 88 MPa,showing excellent tensile strength.The results provide a valuable basis for improving the joint quality of SiC ceramics and metals by adding high-entropy alloy fillers.
文摘A novel super-hybrid composite (NSHC) was boron-modified phenolic resin (BPR) with three-dimensional reticulated SiC ceramic (3DRC) and high silica fibers. Ablation performance of the NSHC was studied. The results show that the linear ablation rate of NSHC was lower than that of pure BPR and the high silica/BPR composite. Its linear ablation rate is 1/17 of the high silica/BPR. Mass ablation rate of the NSHC is very close to that of the pure BPR and the high silica/BPR composite. Scanning electron microscope (SEM) analysis indicates that 3DRC has scarcely changed its shape at the ablation temperature. Its special reticulated structure can restrict the materials deformation and prevent high velocity heat flow from eroding the surface of the materials largely and thus increase ablation resistance of the NSHC.
基金the financial support provided by the National Key R&D Program of China(No.2022YFB3805002)the National Natural Science Foundation of China(No.22308150)+5 种基金Jiangsu Provincial Department of Science and Technology(No.BK20232010)the Research Programs of the Science and Technology of Guangxi Zhuang Autonomous Region(No.GUIKE-AA22117015-1)the Natural Science Foundation of Jiangsu Province(No.BK20220345)the Key R&D Program of Jiangsu Province(No.BE2023360)the Key R&D Project of Nanjing Jiangbei New Area(No.ZDYF202203)the Youth Science and Technology Talents Lifting Project of Jiangsu Association of Science and Technology(No.105019ZS_007).
文摘Porous ceramics usually require high mechanical strength and maximized porosity simultaneously,while for conventional particle grading strategies,it is highly challenging to meet both demands.To this end,a reverse particle grading strategy was developed based on the linear packing model by unusually introducing coarse particles(d_(50)=16μm)into a fine particle(d50=5μm)matrix.Following the extrusion and sintering process,tubular porous SiC ceramic supports with improved mechanical strength were successfully fabricated.The effects of coarse particles on the rheological properties of the ceramic paste and the macroscopic properties and microstructure of the SiC supports were systematically investigated.With an increase in the content of coarse SiC particles to 30 wt%,the pressure generated during extrusion decreased from 5.5±0.2 to 1.3±0.1 MPa.Notably,the bending strength of the tubular supports increased from 36.6±5.6 to 49.1±4.5 MPa when 20 wt%coarse powder was incorporated.The notably improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection.Additionally,the optimized tubular supports had an average pore size of 1.2±0.1μm,an open porosity of 45.1%±1.6%,and a water permeability of 7163±150 L/(m^(2)·h·bar)as well as good alkali and acid corrosion resistance.Significantly,the strategy was proven to be feasible for the scale-up fabrication of 19-channel SiC tubular porous ceramic supports.
文摘This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.
基金supported by the Research Program funded by Seoul National University of Science and Technology(2022-1121).
文摘This study focused on producing metal matrix composite(MMC)coatings on Ti–6Al–4V alloy through laser surface alloying using a novel combination of Inconel 625 and SiC precursor materials.Various ratios of alloying powders were examined to evaluate surface properties such as microhardness,wear resistance,and friction coefficient,along with analyzing the phase composition and microstructure of the coatings.The in situ synthesized MMC coatings exhibited the presence ofα-Ti,NiTi,NiTi_(2),and TiC phases.Additionally,Ti_(5)Si_(3)andα-Ti/Ti_(5)Si_(3)eutectic structures were observed when the SiC content exceeded 20%.In comparison to the titanium substrate,the MMC coating significantly enhanced microhardness by over threefold and reduced wear by 95%.However,it was crucial to carefully select the appropriate combination of alloying powders to avoid a substantial decrease in friction performance and excessive formation of cracks.Through a comparative analysis of experimental results,the optimal precursor material composition was identified as 85%Inconel 625 and 15%SiC.This study demonstrated the effective utilization of Inconel 625 and SiC alloying materials to enhance the surface properties of titanium alloys,thereby expanding their application in challenging environments.
基金supported by the National Key Technology R&D Program of China(Grant No.2011BAE03B07)
文摘Different semiconductive SiC foam supports were prepared by varying the sintering temperature and atmosphere, and with or without alkaline solution treatment and high temperature oxidation following a macromolecule pyrogenation combined with reaction bonding method. Nano-TiO2 particles were immobilized onto these SiC foam supports by a composite sol-gel method. The phase, surface morphology, the type of conduction and the photocatalytic activity of the TiO2-SiC composite photocatalysts were studied. The TiO2 coated on p-type Si-free SiC support showed the highest photocatalytic efficiency in degradation of 4- aminobenzenesulfonic acid （4-ABS） in aqueous solution as compared to that coated on n-type SiC support and p-type SiC supports with residual Si or Si02 on the surface. The result showed that the TiO2 coatings immobilized on p-type semiconductive SiC foam supports exhibited obviously higher photocatalytic activity in comparison to that coated on n-type SiC foam support. The p-n heterojunctions formed between the p-type SiC supports and n-type TiO2 coatings might be able to account for the better charge separation and transfer as well as the photocatalytic activity of the TiO2-SiC composite photocatalyst.
基金supported by the National Key R&D Program of China(No.2017YFB0703201)the National Natural Science Foundation of China(No.51772302)CAS International Cooperation Key Program(No.174321KYSB20180008)。
文摘Model composites consisting of SiC fiber and Yb_(2)SiO_(5)were processed by the spark plasma sintering(SPS)method.The mechanical compatibility and chemical stability between Yb_(2)SiO_(5)and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite(SiC_(f)/SiC CMC).Two kinds of interfaces,namely mechanical and chemical bonding interfaces,were achieved by adjusting sintering temperature.SiC_(f)/Yb_(2)SiO_(5)interfaces prepared at 1450 and 1500℃exhibit high interface strength and debond energy,which do not satisfy the crack deflection criteria based on He-Hutchison diagram.Raman spectrum analyzation indicates that the thermal expansion mismatch between Yb_(2)SiO_(5)and SiC contributes to high compressive thermal stress at interface,and leads to high interfacial parameters.Amorphous layer at interface in model composite sintered at 1550℃is related to the diffusion promoted by high temperature and DC electric filed during SPS.It is inspired that the interfacial parameters could be adjusted by introducing Yb_(2)Si_(2)O_(7)-Yb_(2)SiO_(5)interphase with controlled composition to optimize the mechanical fuse mechanism in SiC_(f)/SiC CMC.
基金support from the National Natural Science Foundation of China(No.52272100)the Natural Science Foundation of Hunan Province(No.2022JJ30662)the Science and Technology on Advanced Ceramic Fibers and Composites Laboratory(No.WDZC20215250507).
文摘Carbide ceramic fibers are of significant importance for application in the high-tech areas of advanced aircraft engines,aerospace vehicles,and the nuclear industry due to their excellent properties,such as high tensile strength and elastic modulus,excellent high-temperature resistance,and oxidation resistance.This paper reviews the preparation and application of different carbide ceramic fibers,including SiC fibers and transition metal carbide(e.g.,ZrC,HfC,and TaC)ceramic fibers.The preparation methods of carbide ceramic fibers are discussed in terms of different fiber diameters,represented by SiC fibers with variable weaving properties and functions due to their differences in diameter.Subsequently,the application of carbide ceramic fibers as high-temperature-resistant structural materials,catalyst carriers,sensors,and supercapacitors are summarized,and strategies for the future development of carbide ceramic fibers are proposed.This review aims to help researchers enhance their understanding of the preparation and utilization of carbide ceramic micro/nanofibers,advancing the development of high-performance carbide ceramic fibers.
